1. Field of the Invention
The present invention relates to dust abatement and filtering apparatus and, more particularly, is directed to dust control apparatus for use in connection with mining machines adapted for mining material from "longwalls" in underground mining operations.
2. Description of the Invention Background
A variety of different apparatuses exist for mining coal and other materials from underground seams. One apparatus which is commonly used in underground mining operations comprises a continuous mining machine which includes a rotatable cutting drum that is mounted on the front end of the mining machine. As the mining machine is advanced into the seam, the cutting drum dislodges or "wins" the coal from the seam. In most continuous miners of this type, the won material is conveyed rearwardly of the cutter drum by a longitudinally extending conveyor that may discharge into shuttle cars or other mobile conveying apparatuses to transport the won material from the mine face. The continuous mining machine continuously advances into the seam and, as the material is won therefrom, an entry or tunnel is formed therein.
Another type of continuous mining machine is used in instances wherein extended portions or longwalls of seam are desired to be mined. Such longwalls may, depending upon the seam configuration, extend for distances of 300-1200 feet. It is standard practice in this type of mining to mine parallel entries into the seam to be mined and connect those entries with one or more primary passages. Such arrangement defines the longwall pillar(s) to be mined. The roof of the primary passages are usually supported by movable roof supports during the mining of the exposed "face" of the longwall pillar.
Conventional longwall mining techniques employ a mining machine that is known in the industry as a longwall shearer. A longwall shearer typically has an elongated mobile frame that is supported on floor-mounted tracks that are adjacent and substantially parallel to the mine face. Rotary driven toothed drums are operably supported on arms on each end of the elongated frame for winning the coal as the frame passes back and forth before the mine face. The won material falls into a face conveyor that is usually attached to the floor-mounted tracks and extends parallel to the longwall face. The face conveyor discharges the material onto other conveying apparatuses to transport the material from the seam. As the mine face recedes, the conveyor and track assembly is advanced forward to enable the shearer to continue mining.
Both of the continuous mining machines discussed above generate dust during the mining process. Dust formation has long been recognized as a serious hazard in underground mining operations and a number of different filtering apparatuses have been developed to control the permeation of airborne dust around the portions of the mining machine where the operators and support personnel are located.
One type of dust control apparatus that has been developed for use with continuous mining machines of the type wherein the cutting drum is mounted on the front end of the machine is disclosed in U.S. Pat. No. 4,380,353 to Campbell et al. That patent discloses a dust control system that includes a series of interconnected ducts with the intakes thereof being located adjacent the cutting drum. A fan is attached to one end of the ductwork for drawing air therein and through a "flooded bed" scrubber. The scrubber comprises a bed formed from a plurality of open mesh material that is housed between reinforcing screens that are mounted in a portion of the ductwork system. A plurality of spray nozzles are mounted upstream of the bed for continuously spraying water thereon. As the dust particles pass through the wet bed, the dust is entrained in droplets of water. A demister, in the form of a collection of louvers, is provided between the bed and the fan and serves to separate the entrained dust particles from the air stream and direct those entrained particles into a sump located therebelow. A pump is provided to pump the dust laden water that collects in the sump to a place of disposal.
While this particular scrubber and ductwork arrangement is adapted for use in connection with continuous mining machines of the type disclosed in the Campbell et al. patent, it is not well-suited for use in connection with longwall shearers, due to the dual cutting drum arrangement and the ventilation air flow that is normally present around the shearer. In particular, in most longwall mining arrangements, it is standard practice to direct ventilation air at relatively high velocities along the longwall face. This air flow tends to circulate around the ends of the shearer and serves to disperse the dust that is generated by the cutting drums in the areas wherein the operating personnel are located. The dust control system disclosed in the Campbell et al. patent is not well adapted for filtering dust laden air from opposite ends of the machine due to the ductwork configuration employed therein.
U.S. Pat. No. 5,219,208 to Liao et al. discloses a scrubber system for dispersing dust that is generated by longwall shearers. The system comprises a plurality of small scrubbing units that are mounted on top of the shearer. Each scrubbing unit contains a series of twin fluid atomizers located at the inlet of the unit to produce a fine mist of water for capturing respirable dust. The scrubbing units are positioned on the shearer such that they can draw the dust cloud from around the rotating drums of the shearer and direct the air containing the water mist and captured dust toward the longwall face. A spray bar equipped with five twin fluid atomizers is mounted adjacent to one of the cutting drums for redirecting dust laden air toward the face. Each of the scrubbing units have fabrication, installation and maintenance costs associated therewith making such system less practical for some shearer configurations. In addition, such dust removal system of this type is somewhat less efficient than the flooded bed type scrubbers which provide a medium wherein the dust laden air and water can be forceably mixed. Thus, there is a need for a dust control system for use with a longwall shearer that is relatively inexpensive to fabricate, install and maintain. There is a further need for a dust control system that can efficiently remove airborne dust from around those portions of the shearer wherein the operating personnel are typically located.
The subject invention is directed toward an improved apparatus for removing dust created during mining by a longwall shearer which addresses, among others, the above-discussed needs and provides a dust control apparatus which is effective in preventing dust flow in operator areas and removing dust particles from ventilation air.